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Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs

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ABSTRACT

Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

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AFM images of AlGaAs surfaces after LDE with Al droplets at varied parameters. a Sample with T=605 °C, θAl=1.4 ML, and PAs≃6×10−8 Torr. b Like a but with an additional 670 °C pre-growth overheating step. c Sample with T=550 °C, fully minimized PAs≃1×10−10 Torr, θAl=1.0 ML, and no overheating. d Like c but with overheating
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Fig1: AFM images of AlGaAs surfaces after LDE with Al droplets at varied parameters. a Sample with T=605 °C, θAl=1.4 ML, and PAs≃6×10−8 Torr. b Like a but with an additional 670 °C pre-growth overheating step. c Sample with T=550 °C, fully minimized PAs≃1×10−10 Torr, θAl=1.0 ML, and no overheating. d Like c but with overheating

Mentions: This study focuses on LDE with Al droplets to form low-density nanoholes in (001) AlGaAs surfaces. An example is shown in Fig. 1a. The nanohole depth can be tuned by the amount of deposited droplet material and the process temperature from 1 nm up to more than 100 nm [15]. By hole filling with a material different from the substrate, droplet-etched nanoholes represent an interesting template for the self-assembled creation of, e.g., strain-free GaAs quantum dots [13] or nanopillars for thermoelectrics [14].Fig. 1


Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs
AFM images of AlGaAs surfaces after LDE with Al droplets at varied parameters. a Sample with T=605 °C, θAl=1.4 ML, and PAs≃6×10−8 Torr. b Like a but with an additional 670 °C pre-growth overheating step. c Sample with T=550 °C, fully minimized PAs≃1×10−10 Torr, θAl=1.0 ML, and no overheating. d Like c but with overheating
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037105&req=5

Fig1: AFM images of AlGaAs surfaces after LDE with Al droplets at varied parameters. a Sample with T=605 °C, θAl=1.4 ML, and PAs≃6×10−8 Torr. b Like a but with an additional 670 °C pre-growth overheating step. c Sample with T=550 °C, fully minimized PAs≃1×10−10 Torr, θAl=1.0 ML, and no overheating. d Like c but with overheating
Mentions: This study focuses on LDE with Al droplets to form low-density nanoholes in (001) AlGaAs surfaces. An example is shown in Fig. 1a. The nanohole depth can be tuned by the amount of deposited droplet material and the process temperature from 1 nm up to more than 100 nm [15]. By hole filling with a material different from the substrate, droplet-etched nanoholes represent an interesting template for the self-assembled creation of, e.g., strain-free GaAs quantum dots [13] or nanopillars for thermoelectrics [14].Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

No MeSH data available.


Related in: MedlinePlus